The motors spin the focus/zoom rings through a belt system - no lens gears required. My guess is you should be using a lens that has a smooth and easy to rotate focus or zoom ring. The rear holds a master controller that can be used to operate the motors when the shoulder rig is tripod mounted. The motors are powered by an LP-E6 battery (generic LP-E6 battery + charger included), and can be found via eBay (click here).